diff options
Diffstat (limited to 'recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch')
| -rw-r--r-- | recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch | 125 |
1 files changed, 0 insertions, 125 deletions
diff --git a/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch b/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch deleted file mode 100644 index 3cd07c0a..00000000 --- a/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch +++ /dev/null @@ -1,125 +0,0 @@ -From 5e6dca82bcaa49348f9e5fcb48df4881f6d6c4ae Mon Sep 17 00:00:00 2001 -From: Nick Desaulniers <ndesaulniers@google.com> -Date: Tue, 12 Jan 2021 11:46:24 -0800 -Subject: [PATCH] x86/entry: Emit a symbol for register restoring thunk - -Arnd found a randconfig that produces the warning: - - arch/x86/entry/thunk_64.o: warning: objtool: missing symbol for insn at - offset 0x3e - -when building with LLVM_IAS=1 (Clang's integrated assembler). Josh -notes: - - With the LLVM assembler not generating section symbols, objtool has no - way to reference this code when it generates ORC unwinder entries, - because this code is outside of any ELF function. - - The limitation now being imposed by objtool is that all code must be - contained in an ELF symbol. And .L symbols don't create such symbols. - - So basically, you can use an .L symbol *inside* a function or a code - segment, you just can't use the .L symbol to contain the code using a - SYM_*_START/END annotation pair. - -Fangrui notes that this optimization is helpful for reducing image size -when compiling with -ffunction-sections and -fdata-sections. I have -observed on the order of tens of thousands of symbols for the kernel -images built with those flags. - -A patch has been authored against GNU binutils to match this behavior -of not generating unused section symbols ([1]), so this will -also become a problem for users of GNU binutils once they upgrade to 2.36. - -Omit the .L prefix on a label so that the assembler will emit an entry -into the symbol table for the label, with STB_LOCAL binding. This -enables objtool to generate proper unwind info here with LLVM_IAS=1 or -GNU binutils 2.36+. - - [ bp: Massage commit message. ] - -Reported-by: Arnd Bergmann <arnd@arndb.de> -Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> -Suggested-by: Borislav Petkov <bp@alien8.de> -Suggested-by: Mark Brown <broonie@kernel.org> -Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> -Signed-off-by: Borislav Petkov <bp@suse.de> -Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> -Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> -Link: https://lkml.kernel.org/r/20210112194625.4181814-1-ndesaulniers@google.com -Link: https://github.com/ClangBuiltLinux/linux/issues/1209 -Link: https://reviews.llvm.org/D93783 -Link: https://sourceware.org/binutils/docs/as/Symbol-Names.html -Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1408485ce69f844dcd7ded093a8 [1] - -Upstream-Status: Backport -Signed-off-by: Anuj Mittal <anuj.mittal@intel.com> ---- - Documentation/asm-annotations.rst | 5 +++++ - arch/x86/entry/thunk_64.S | 8 ++++---- - include/linux/linkage.h | 5 +++++ - 3 files changed, 14 insertions(+), 4 deletions(-) - -diff --git a/Documentation/asm-annotations.rst b/Documentation/asm-annotations.rst -index 32ea57483378d..76424e0431f4b 100644 ---- a/Documentation/asm-annotations.rst -+++ b/Documentation/asm-annotations.rst -@@ -100,6 +100,11 @@ Instruction Macros - ~~~~~~~~~~~~~~~~~~ - This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above. - -+``objtool`` requires that all code must be contained in an ELF symbol. Symbol -+names that have a ``.L`` prefix do not emit symbol table entries. ``.L`` -+prefixed symbols can be used within a code region, but should be avoided for -+denoting a range of code via ``SYM_*_START/END`` annotations. -+ - * ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the - most frequent markings**. They are used for functions with standard calling - conventions -- global and local. Like in C, they both align the functions to -diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S -index ccd32877a3c41..c9a9fbf1655f3 100644 ---- a/arch/x86/entry/thunk_64.S -+++ b/arch/x86/entry/thunk_64.S -@@ -31,7 +31,7 @@ SYM_FUNC_START_NOALIGN(\name) - .endif - - call \func -- jmp .L_restore -+ jmp __thunk_restore - SYM_FUNC_END(\name) - _ASM_NOKPROBE(\name) - .endm -@@ -44,7 +44,7 @@ SYM_FUNC_END(\name) - #endif - - #ifdef CONFIG_PREEMPTION --SYM_CODE_START_LOCAL_NOALIGN(.L_restore) -+SYM_CODE_START_LOCAL_NOALIGN(__thunk_restore) - popq %r11 - popq %r10 - popq %r9 -@@ -56,6 +56,6 @@ SYM_CODE_START_LOCAL_NOALIGN(.L_restore) - popq %rdi - popq %rbp - ret -- _ASM_NOKPROBE(.L_restore) --SYM_CODE_END(.L_restore) -+ _ASM_NOKPROBE(__thunk_restore) -+SYM_CODE_END(__thunk_restore) - #endif -diff --git a/include/linux/linkage.h b/include/linux/linkage.h -index 5bcfbd972e970..dbf8506decca0 100644 ---- a/include/linux/linkage.h -+++ b/include/linux/linkage.h -@@ -178,6 +178,11 @@ - * Objtool generates debug info for both FUNC & CODE, but needs special - * annotations for each CODE's start (to describe the actual stack frame). - * -+ * Objtool requires that all code must be contained in an ELF symbol. Symbol -+ * names that have a .L prefix do not emit symbol table entries. .L -+ * prefixed symbols can be used within a code region, but should be avoided for -+ * denoting a range of code via ``SYM_*_START/END`` annotations. -+ * - * ALIAS -- does not generate debug info -- the aliased function will - */ - |